Targeting AKT/mTOR and ERK MAPK signaling inhibits homon-refractory prostate cancer in a preclinical mouse model

Department of Urology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
Journal of Clinical Investigation (Impact Factor: 13.22). 10/2008; 118(9):3051-64. DOI: 10.1172/JCI34764
Source: PubMed


The AKT/mammalian target of rapamycin (AKT/mTOR) and ERK MAPK signaling pathways have been shown to cooperate in prostate cancer progression and the transition to androgen-independent disease. We have now tested the effects of combinatorial inhibition of these pathways on prostate tumorigenicity by performing preclinical studies using a genetically engineered mouse model of prostate cancer. We report here that combination therapy using rapamycin, an inhibitor of mTOR, and PD0325901, an inhibitor of MAPK kinase 1 (MEK; the kinase directly upstream of ERK), inhibited cell growth in cultured prostate cancer cell lines and tumor growth particularly for androgen-independent prostate tumors in the mouse model. We further showed that such inhibition leads to inhibition of proliferation and upregulated expression of the apoptotic regulator Bcl-2-interacting mediator of cell death (Bim). Furthermore, analyses of human prostate cancer tissue microarrays demonstrated that AKT/mTOR and ERK MAPK signaling pathways are often coordinately deregulated during prostate cancer progression in humans. We therefore propose that combination therapy targeting AKT/mTOR and ERK MAPK signaling pathways may be an effective treatment for patients with advanced prostate cancer, in particular those with hormone-refractory disease.

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Available from: Mireia Castillo-Martin
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    • "In preclinical breast and prostate cancer murine models, inhibition of mTORC1, which is composed of regulatoryassociated protein of mTOR (RAPTOR), mLST8 (also known as GbL), and AKT substrate of 40 kDa (PRAS40), with the mTORi rapamycin, led to MAPK pathway activation through a PI3K- dependent feedback loop. However, when rapamycin was combined with the MEK1/2 inhibitor, PD0325901, MAPK feedback activation was abrogated and resulted in an enhanced antitumoral effect (Carracedo et al, 2008; Kinkade et al, 2008). "
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    ABSTRACT: The MEK inhibitor, selumetinib, suppresses soft-tissue sarcoma (STS) cell proliferation in vitro. Mammalian target of rapamycin inhibitors possess modest activity against STS; however, resistance develops via MAPK pathway feedback activation. The combination of selumetinib and temsirolimus synergistically inhibits STS cell line growth. Therefore, a randomized phase II trial of selumetinib vs selumetinib plus temsirolimus was conducted. Seventy-one adults with advanced STS who received ⩽2 prior chemotherapeutics were randomized to selumetinib 75 mg p.o. bid and allowed to crossover upon progression, or to selumetinib 50 mg p.o. bid plus temsirolimus 20 mg i.v. weekly, with primary endpoint of progression-free survival (PFS). There was no difference in PFS between the two arms for the overall cohort (median 1.9 vs 2.1 months); an improved median PFS was observed in the combination arm (N=11) over single agent (N=10) in the prespecified leiomyosarcoma stratum (median 3.7 vs 1.8 months; P=0.01). Four-month PFS rate was 50% (95% confidence interval 0.19-0.81) with the combination vs 0% with selumetinib alone in the leiomyosarcoma cohort. Most common grade 3/4 adverse events with the combination were mucositis (29%), lymphopenia (26%), neutropenia and anaemia (20% each). While single-agent selumetinib has no significant activity in STS, the combination may be active for leiomyosarcomas.British Journal of Cancer advance online publication, 21 April 2015; doi:10.1038/bjc.2015.126
    Full-text · Article · Apr 2015 · British Journal of Cancer
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    • "Akt1: S473 [15,16] "
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    ABSTRACT: Background Although recent progress has been made in treating castration resistant prostate cancer, the interplay of signaling pathways which enable castration resistant growth is incompletely understood. A data driven, multivariate approach, was used in this study to predict prostate cancer cell survival based on the phosphorylation levels of key proteins in PC3, LNCaP, and MDA-PCa-2b cell lines in response to EGF, IGF1, IL6, TNFα, dihydrotestosterone, and docetaxel treatment. Methods The prostate cancer cell lines were treated with ligands or inhibitors, cell lyates were collected, and the amount of phosphoprotein quantified using 384 well ELISA assays. In separate experiments, relative cell viability was determined using an MTT assay. Normalized data was imported into Matlab where regression analysis was performed. Results Based on a linear model developed using partial least squares regression, p-Erk1/2 was found to correlate with castration resistant survival along with p-RPS6, and this model was determined to have a leave-one-out cross validated R2 value of 0.61. The effect of androgen on the phosphoproteome was examined, and increases in PI3K related phosphoproteins (p-Akt, p-RPS6, and p-GSK3) were observed which accounted for the majority of the significant increase in androgen-mediated cell survival. Simultaneous inhibition of the PI3K pathway and treatment with androgen resulted in a non-significant increase in survival. Given the strong effect of PI3K related signaling in enabling castration resistant survival, the specific effect of mTor versus complete inhibition was examined using targeted inhibitors. It was determine that mTor inhibition accounts for 52% of the effect of complete PI3K inhibition on cell survival. The differences in signaling between the cell lines were explored it was observed that MDA-PCa-2b exhibited far less activation of p-Erk in response to varying treatments, explaining one of the reasons for the lack of castration resistance. Conclusion In this work, regression analysis to the phosphoproteome was used to illustrate the sources of castration resistance between the cell lines including reduced p-Erk signaling in MDA-PCa-2b and variations in p-JNK across the cell lines, as well as studying the signaling pathways which androgen acts through, and determining the response to treatment with targeted inhibitors.
    Full-text · Article · May 2014 · BMC Cancer
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    • "For example, combined PI3K and mTOR inhibition with the dual kinase inhibitor BEZ235 reduced tumor volumes in a mouse model of PCa mediated by PTEN loss, demonstrating a continued requirement for pathway hyperactivity to maintain established tumors.27 Moreover, others have demonstrated that allosteric inhibitors of mTOR (rapalogues) such as rapamycin and everolimus also exhibit antitumor efficacy in established murine PCas.727475 As such, these studies prompted significant efforts to determine the clinical role of allosteric inhibitors of mTOR in advanced human PCa. "
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    ABSTRACT: Prostate cancer (PCa) is the second most common malignancy among men in the world. Castration-resistant prostate cancer (CRPC) is the lethal form of the disease, which develops upon resistance to first line androgen deprivation therapy (ADT). Emerging evidence demonstrates a key role for the PI3K-AKT-mTOR signaling axis in the development and maintenance of CRPC. This pathway, which is deregulated in the majority of advanced PCas, serves as a critical nexus for the integration of growth signals with downstream cellular processes such as protein synthesis, proliferation, survival, metabolism and differentiation, thus providing mechanisms for cancer cells to overcome the stress associated with androgen deprivation. Furthermore, preclinical studies have elucidated a direct connection between the PI3K-AKT-mTOR and androgen receptor (AR) signaling axes, revealing a dynamic interplay between these pathways during the development of ADT resistance. Thus, there is a clear rationale for the continued clinical development of a number of novel inhibitors of the PI3K pathway, which offer the potential of blocking CRPC growth and survival. In this review, we will explore the relevance of the PI3K-AKT-mTOR pathway in PCa progression and castration resistance in order to inform the clinical development of specific pathway inhibitors in advanced PCa. In addition, we will highlight current deficiencies in our clinical knowledge, most notably the need for biomarkers that can accurately predict for response to PI3K pathway inhibitors.
    Full-text · Article · Apr 2014 · Asian Journal of Andrology
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